@sap/cds-dk/lib/mtx/util/urls.js

Command line client and development toolkit for the SAP Cloud Application Programming Model

const IP_ADDR = /^[1-9][0-9]{0,2}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}$/;
const schemaRegex = /^https?:\/\//;
const localhostRegex = /^(https?:\/\/)?(localhost|127\.0\.0\.1|\[?::1]?)\b/;
const httpSchema = 'http://';
const httpsSchema = 'https://';

function extractSubdomain(url) {
    const hostname = new URL(url).hostname;
    if (localhostRegex.test(hostname) || IP_ADDR.test(hostname)) {
        return undefined;
    }
    return hostname.split('.')[0];
}

function concatUrls(...parts) {
    return parts
        .map((p, i) => i === 0
            ? p.replace(/\/$/ /*end slash*/, '')
            : i === parts.length - 1
                ? p.replace(/^\// /*begin slash*/, '')
                : p.replace(/^\/|\/$/g /*both*/, ''))
        .join('/');
}

module.exports = {
    schemaRegex,
    localhostRegex,
    httpSchema,
    httpsSchema,
    extractSubdomain,
    concatUrls
};